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INTRODUCTION

This discussion covers only two sections of 29 CFR 1910.106:

Container and portable tank storage, and

Industrial plants.

The primary basis of this standard is the National Fire Protection
Association's publication NFPA 30, Flammable and Combustible Liquids Code. 29 CFR 1910.106 applies
to the handling, storage, and use of flammable and combustible liquids with a flash point below
200ºF.

There are two primary hazards associated with flammable and combustible liquids: explosion and fire.
In order to prevent these hazards, this standard addresses the primary concerns of: design and
construction, ventilation, ignition sources, and storage.

There are a number of definitions included in 29 CFR1910.106. These definitions were derived from
consensus standards, and were not uniquely developed for OSHA standards. Some of the more important
definitions are discussed below.

Aerosol: a material which is dispensed from its container as a mist,
spray, or foam by a propellant under pressure.

Approved: approved or listed by a nationally recognized testing
laboratory.

Boiling point: the boiling point of a liquid at a pressure of 14.7 pounds
per square inch absolute (psia). This pressure is equivalent to 760 millimeters of mercury (760 mm
Hg).

At temperatures above the boiling point, the pressure of the atmosphere can no longer hold the
liquid in the liquid state and bubbles begin to form. The lower the boiling point, the greater the
vapor pressure at normal ambient temperatures and consequently the greater the fire risk.

Container: any can, barrel, or drum.

Closed container: a container so sealed by means of a lid or other device
that neither liquid nor vapor will escape from it at ordinary temperatures.

Fire area: area of a building separated from the remainder of the building
by construction having a fire resistance of at least 1 hour and having all communicating openings
properly protected by an assembly having a fire resistance rating of at least 1 hour.

Flash point: the minimum temperature at which a liquid gives off vapor
within a test vessel in sufficient concentration to form an ignitable mixture with air near the
surface of the liquid. The flash point is normally an indication of susceptibility to ignition.

The flash point is determined by heating the liquid in test equipment and measuring the temperature
at which a flash will be obtained when a small flame is introduced in the vapor zone above the
surface of the liquid.

A standard closed container is used to determine the closed-cup flash point and a standard
open-surface dish for the open-cup flash point temperature, as specified by the American Society for
Testing and Materials (ASTM). These methods are referenced in OSHA's 1910.106 standard.

Combustible liquid: any liquid having a flash point at or above 100ºF
(37.8ºC).

Combustible liquids shall be divided into two classes as follows:

Class II liquids shall include those with
flash points at or above 100ºF (37.8ºC) and below 140ºF (60ºC), except any mixture having
components with flash points of 200ºF (93.3ºC) or higher, the volume of which make up 99 percent
or more of the total volume of the mixture.

Class III liquids shall include those
with flash points at or above 140ºF (60ºC). Class III liquids are subdivided into two subclasses:

Class IIIA liquids shall include those
with flash points at or above 140ºF (60ºC) and below 200ºF (93.3ºC), except any mixture having
components with flash points of 200ºF (93.3ºC), or higher, the total volume of which make up 99
percent or more of the total volume of the mixture.

Class IIIB liquids shall include those
with flash points at or above 200ºF (93.3ºC). This section does not regulate Class IIIB liquids.
Where the term "Class III liquids" is used in this section, it shall mean only Class IIIA
liquids.

When a combustible liquid is heated to within 30ºF (16.7ºC) of its flash
point, it shall be handled in accordance with the requirements for the next lower class of liquids.

Flammable liquid: any liquid having a flash point below 100ºF (37.8ºC),
except any mixture having components with flashpoints of 100ºF (37.8ºC) or higher, the total of
which make up 99 percent or more of the total volume of the mixture. Flammable liquids shall be
known as Class I liquids. Class I liquids are divided into three classes as follows:

Class IA shall include liquids having flash points below 73ºF
(22.8ºC) and having a boiling point below 100ºF (37.8ºC).

Class IB shall include liquids having flash points below 73ºF
(22.8ºC) and having a boiling point at or above 100ºF (37.8ºC).

It should be mentioned that flash point was selected as the basis for
classification of flammable and combustible liquids because it is directly related to a liquid's
ability to generate vapor, i.e., its volatility. Since it is the vapor of the liquid, not the liquid
itself that burns, vapor generation becomes the primary factor in determining the fire hazard. The
expression "low flash - high hazard" applies. Liquids having flash points below ambient storage
temperatures generally display a rapid rate of flame spread over the surface of the liquid, since it
is not necessary for the heat of the fire to expend its energy in heating the liquid to generate
more vapor.

The above definitions for classification of flammable and combustible liquids are quite complex. The
diagram below should aid in their understanding.

Classes of Flammable and Combustible Liquids
as Defined by 29 CFR 1910.106

Portable tank: a closed container having a liquid capacity over 60 U.S. gallons and
not intended for fixed installation.

Safety Can

Safety can: an approved container, of not more than 5 gallons
capacity, having a spring-closing lid and spout cover and so designed that it will safely
relieve internal pressure when subjected to fire exposure.

Vapor pressure: the pressure, measured in pounds per square inch (absolute)
exerted by a volatile liquid as determined by the Standard Method of Test for Vapor
Pressure of Petroleum Products (Reid Method), American Society for Testing and
Materials ASTM D323-68.

Vapor pressure is a measure of a liquid's propensity to evaporate. The higher the
vapor pressure, the more volatile the liquid and, thus, the more readily the liquid gives
off vapors.

Ventilation as specified in this section is for the prevention of fire and explosion. It is
considered adequate if it is sufficient to prevent accumulation of significant quantities
of vapor-air mixtures in concentration over one-fourth of the lower flammable limit.

When vapors of a flammable or combustible liquid are mixed with air in the proper
proportions in the presence of a source of ignition, rapid combustion or an explosion
can occur. The proper proportion is called the flammable range
and is also often referred to as the explosive range. The
flammable range includes all concentrations of flammable vapor or gas in air, in which
a flash will occur or a flame will travel if the mixture is ignited. There is a minimum
concentration of vapor or gas in air below which propagation of flame does not occur on
contact with a source of ignition. There is also a maximum proportion of vapor in air
above which propagation of flame does not occur. These boundary-line mixtures of vapor
with air are known as the lower and upper flammable limits (LFL or UFL)
respectively, and they are usually expressed in terms of percentage by volume of vapor in air.
See figure below.

In popular jargon, a vapor/air mixture below the lower flammable limit is too "lean" to
burn or explode, and a mixture above the upper flammable limit is too "rich" to burn
or explode. The LFL is also known as the lower explosive limit (LEL).
The UFL is also referred to as the upper explosive limit (UEL).
No attempt is made to differentiate between the terms flammable
and explosive as applied to the lower and upper limits of flammability.

This section applies only to the storage of flammable or combustible liquids in drums
or other containers (including flammable aerosols) not exceeding 60 gallons individual
capacity and portable tanks of less than 660 gallon individual capacity. A portable
tank is a closed container which has a liquid capacity of over 60 gallons and is not
intended for fixed installations.

This section does not apply to the following:

Storage of containers in bulk plants, service stations, refineries, chemical plants,
and distilleries;

Class I or Class II liquids in the fuel tanks of a motor vehicle, aircraft, boat, or
portable or stationary engine;

Flammable or combustible paints, oils, varnishes, and similar mixtures used for
painting or maintenance when not kept for a period in excess of 30 days;

Beverages when packed in individual containers not exceeding 1 gallon in size.

Design, Construction, and Capacity of Containers

Only approved containers and portable tanks may be used to store flammable and
combustible liquids. Metal containers and portable tanks meeting the requirements of
the Department of Transportation (DOT) (49 CFR 178) are deemed acceptable when
containing products authorized by the DOT (49 CFR 173).

29 CFR 1910.106 also requires portable tanks to have provision for emergency
venting. Top-mounted emergency vents must be capable of limiting internal pressure
under fire exposure conditions to 10 psig or 30 percent of the bursting pressure of the
tank, whichever is greater. Portable tanks are also required to have at least one
pressure-activated vent with a minimum capacity of 6,000 cubic feet of free air at 14.7
psia and 60ºF. These vents must be set to open at not less than 5 psig. If fusible
vents are used, they shall be actuated by elements that operate at a temperature not exceeding 300ºF.

Maximum allowable sizes of various types of containers and portable tanks are specified based on the
class of flammable and combustible liquid they contain.

Design, Construction and Capacity of Storage Cabinets

Properly labeled storage cabinet

Not more than 60 gallons of Class I and/or Class II liquids, or not more than 120 gallons
of Class III liquids may be stored in an individual cabinet

This standard permits both metal and wooden storage cabinets. Storage cabinets shall be designed and
constructed to limit the internal temperature to not more than 325ºF when subjected to a
standardized 10-minute fire test. All joints and seams shall remain tight and the door shall remain
securely closed during the fire test. Storage cabinets shall be conspicuously labeled, "Flammable -
Keep Fire Away."

The bottom, top, door, and sides of metal cabinets shall be at least No. 18 gage sheet metal and
double walled with 1½-inch air space. The door shall be provided with a three-point lock, and the
door sill shall be raised at least 2 inches above the bottom of the cabinet.

Design and Construction of Inside Storage Rooms

Construction

Construction is to comply with the test specifications included in NFPA 251-1969, Standard Methods
of Fire Tests of Building Construction and Materials.

Openings to other rooms or buildings shall be provided with non-combustible liquidtight raised sills
or ramps at least 4 inches in height, or the floor in the storage area shall be at least 4 inches
below the surrounding floor. Openings shall be provided with approved self-closing fire doors. The
room shall be liquid-tight where the walls join the floor. A permissible alternate to the sill or
ramp is an open-grated trench inside of the room which drains to a safe location. This method may be
preferred if there is an extensive need to transfer flammable liquids into and out of the room by
means of hand trucks.

Electrical wiring and equipment located in inside storage rooms used for Class I liquids shall be
approved under Subpart S, Electrical, for Class I, Division 2 Hazardous Locations; for Class II and
Class III liquids, shall be approved for general use.

Ventilation

Every inside storage room shall be provided with either a gravity or a mechanical exhaust
ventilation system designed to provide for a complete change of air within the room at least six
times per hour. Ventilation is vital to the prevention of flammable liquid fires and explosions. It
is important to ensure that air flow through the system is constant and prevents the accumulation of
any flammable vapors.

Storage

In every inside storage room, there shall be maintained an aisle at least 3 feet wide. Easy movement
within the room is necessary in order to reduce the potential for spilling or damaging the
containers and to provide both access for fire fighting and a ready escape path for occupants of the
room, should a fire occur.

Containers over 30 gallons capacity shall not be stacked one upon the other. Such containers are
built to DOT specifications and are not required to withstand a drop test greater than 3 feet when
full.

Dispensing shall be only by approved pump or self-closing faucet.

Storage Inside Building

Egress

Flammable or combustible liquids, including stock for sale, shall not be stored so as to limit use
of exits, stairways, or areas normally used for the safe egress of people.

Office Occupancies

Storage shall be prohibited except that which is required for maintenance and operation of
equipment. Such storage shall be kept in closed metal containers stored in a storage cabinet or in
safety cans or in an inside storage room not having a door that opens into that portion of the
building used by the public.

General Purpose Public Warehouses

There are tables in the standard summarizing the storage requirements applicable to "General Purpose
Public Warehouses." These tables refer to indoor storage of flammable and combustible liquids which
are confined in containers and portable tanks. Storage of incompatible materials that create a fire
exposure (e.g., oxidizers, water-reactive chemicals, certain acids and other chemicals) is not
permitted.

Warehouses or Storage Buildings

The last type of inside storage covered by this paragraph addresses storage in "warehouses or
storage buildings." These structures are sometimes referred to as outside storage rooms. Practically
any quantity of flammable and combustible liquid can be stored in these buildings provided that they
are stored in a configuration consistent with the tables in this paragraph.

Containers in piles shall be separated by pallets or dunnage where necessary to provide stability
and to prevent excessive stress on container walls.

Stored material shall not be piled within 3 feet of beams or girders and shall be at least 3 feet
below sprinkler deflectors or discharge orifices of water spray, or other fire protection equipment.

Aisles of at least 3 feet in width shall be maintained to access doors, windows or standpipe
connections.

Storage Outside Buildings

Requirements covering "storage outside buildings" are summarized in tables in this paragraph.
Associated requirements are given for storage adjacent to buildings. Also included are requirements
involving controls for diversion of spills away from buildings and security measures for protection
against trespassing and tampering. Certain housekeeping requirements are given which relate to
control of weeds, debris and accumulation of unnecessary combustibles.

Fire Control

Suitable fire control devices, such as small hose or portable fire extinguishers, shall be available
at locations where flammable or combustible liquids are stored.

At least one portable fire extinguisher having a rating of not less than 12-B units shall be
located:

outside of, but not more than 10 feet from, the door opening into any room used for storage; and

not less than 10 feet, nor more than 25 feet, from any Class I or Class II liquid storage area
located outside of a storage room but inside a building.

The reason for requiring that portable fire extinguishers be located a distance away from the
storage room is that fires involving Class I and Class II flammable liquids are likely to escalate
rapidly. If the fire is too close to the storage area, it may be impossible to get to it once the
fire has started.

Open flames and smoking shall not be permitted in flammable or combustible liquid storage areas.

Materials which react with water shall not be stored in the same room with flammable or combustible
liquids. Many flammable and combustible liquid storage areas are protected by automatic sprinkler or
water spray systems and hose lines. Consequently, any storage of water-reactive material in the
storage area creates an unreasonable risk.

the use of flammable or combustible liquids is incidental to the principal business; or

flammable or combustible liquids are handled or used only in unit physical operations such as
mixing, drying, evaporating, filtering, distillation, and similar operations which do not involve
chemical reaction.

This paragraph shall not apply to chemical plants, refineries or distilleries.

Incidental Storage or Use of Flammable or Combustible Liquids

Application

This subparagraph is applicable to those portions of an industrial plant where the use and handling
of flammable or combustible liquids is only incidental to the principal business, such as paint
thinner storage in an automobile assembly plant, solvents used in the construction of electronic
equipment, and flammable finishing materials used in furniture manufacturing.

Containers

Flammable or combustible liquids shall be stored in tanks or closed containers.

The quantity of liquid that may be located outside of an inside storage room or storage cabinet in a
building or in any one fire area of a building shall not exceed:

25 gallons of Class IA liquids in containers

120 gallons of Class IB, IC, II, or III liquids in containers

660 gallons of Class 1B, 1C, II, or III liquids in a single portable tank.

Handling Liquids at Point of Final Use

Flammable liquids shall be kept in covered containers when not actually in use. Where flammable or
combustible liquids are used or handled, except in closed containers, means shall be provided to
dispose promptly and safely of leakage or spills.

Flammable or combustible liquids shall be drawn from or transferred into vessels, containers, or
portable tanks within a building only in the following manner:

(1) Through a closed piping system,

(2) From safety cans,

(3) By means of a device drawing through the top, or

(4) From containers or portable tanks by gravity through an approved self-closing valve.

Transfer operations must be provided with adequate ventilation. Sources of ignition are not
permitted in areas where flammable vapors may travel.

Transferring liquids by means of air pressure on the container or portable tanks is prohibited. This
may result in an overpressure which could exceed what the container or tank could withstand. In
addition, a flammable atmosphere could be created within the container or tank. This atmosphere
would be particularly sensitive to ignition because of the increased pressure.

____________________________________________________1Fire protection system shall be sprinkler, water spray, carbon dioxide, or other system.